Treatment devices of this kind for microscopic samples are known per se from the prior art. They might be, in particular, an automatic embedding device, an automatic staining device and/or an automatic covering device. The treatment device may consequently consist of one or more such devices. In the simplest case, the treatment device therefore consists for example of an automatic embedding device which prepares a sample for a subsequent microtome section in a plurality of process steps. A tissue processor of this kind for biological or histological samples is known from DE 10 2005 057 191 A1. The same applies to an automatic staining device and an automatic covering device. These devices may also be combined to form one piece of equipment. A treatment device for the purposes of the present application may thus also be a combined apparatus of this kind, i.e. a combined automatic staining and covering device, for example, in which a sample is processed in a number of process steps, while in this case the samples first pass through the automatic staining device and then through the automatic covering device for applying cover slips to the stained sample.
With regard to the structure and mode of operation of automatic staining and covering devices per se and in combination with one another, reference is explicitly made to German Patent no. DE 101 44 989 B4 which relates to a system for processing specimens mounted on slides for subsequent microscopic examination, this system comprising an autonomously operating automatic staining device for staining the specimens, which is configured separately in a housing, a plurality of slides being arranged in a rack and passing through the staining process in this rack. In addition, the system comprises a transporting device for transporting the rack within the automatic staining device and a separately configured and autonomously operating automatic covering device for applying cover slips to the stained specimens. The automatic staining device and automatic covering device are arranged side by side and contain lateral openings facing one another, through which a transporting device configured as a robot arm is able to transfer a rack from the automatic staining device directly into the automatic covering device. Regarding the exact sequence of the independent process steps through which a microscopic sample passes, reference is once again made to this specification.
Similar systems for staining and covering microscopic samples on slides are known from DE 101 44 042 A1 and from DE 201 22 727 U.
Embedding devices, also known as automatic embedding devices or tissue processors, are used in routine clinical diagnostics for preparing samples for microscopic examination.
To obtain thin, uniform microtome sections in histopathology, the material that is to be examined must have stability and a uniform consistency or strength. For this reason, tissue infiltration with hot paraffin wax (hereinafter also generally referred to as “paraffin”) is frequently carried out.
As paraffin is insoluble in water, tissue (for example formalin-fixed) is first dehydrated as gently as possible in an increasing alcohol series (with an increasing concentration of methanol or ethanol). After the dehydration the alcohol from the last dehydration step, which is as anhydrous as possible, is removed using a so-called intermedium (e.g. xylene or a xylene mixture) that is particularly readily miscible with paraffin and additionally absorbs the last remnants of water. The intermedium is then replaced by hot paraffin wax, often by vacuum infiltration.
The paraffin-impregnated pieces of tissue can then be processed into cuttable paraffin blocks, then sliced and transferred onto slides. After deparaffination, staining, covering, etc., the sections are available for examination under a microscope.
A tissue processor which allows substantially automatic processing of samples is shown and described in the Leica publication “Leica ASP 300”, Leica Microsystems NuBloch GmbH, Order No. 0704-2-1-103, 04/2001. The tissue processor comprises a retort as the processing station for the samples. The retort is connected to a number of standardised reagent storage containers via a system of tubes or pipes. The respective reagents can be automatically pumped from the storage containers into the retort and back by a pumping system with an electronic control.
Even though the present invention is described within the scope of this application predominantly in relation to paraffin infiltration, it is also suitable for other infiltration methods, for example for embedding in synthetic resin.
The embedding process described previously has a number of critical steps or process variables.
As already mentioned, the residual water in the tissue sample that is to be embedded has to be removed as completely as possible before the infiltration, on account of the poor miscibility of water and paraffin wax, as otherwise the cuttability and sample quality would be adversely affected. However, in practice, water is often entrained from the less concentrated stages of the alcohol gradient into the pure alcohol of the final dehydration stage. Also, the final alcohol stage often contains residual water because of the hygroscopic properties of ethanol, for example.
Certainly, residual water can be partially removed from the tissue samples by the intermedium, as already mentioned. However, in the interests of the highest possible reproducibility and process certainty, care must be taken to ensure that the desired concentrations of the components of the alcohol series are adhered to as accurately as possible. For this purpose, as disclosed in the as yet unpublished applications DE 10 2008 054 071 and DE 10 2008 054 066, thereof may be a concentration and/or purity of a process medium and/or a characteristic property determined.
Xylene which is frequently used as an intermedium is flammable and is harmful to health when absorbed through the skin and airways. In a volume of 1-8% in air, xylene forms explosive mixtures. Xylene contamination from the intermedium used must therefore be kept to a minimum as far as possible. Entrainment problems may also occur during the transfer from the intermedium to the infiltration medium, leading to an increasing xylene concentration in the paraffin wax used subsequently.
When the embedded sample is taken out of the tissue processor at the end of the treatment the user is therefore exposed to possibly harmful xylene vapours. Too high a xylene concentration in the infiltration medium can also adversely affect the sample quality and subsequent cuttability.
Therefore, every effort is made to minimise the xylene concentration in the paraffin, at least in the sample removed at the end. This can be done, for example, using a process for processing tissue samples in which, between the xylene or intermedium treatment step and the treatment of the tissue samples with a carrier material (such as paraffin wax), a carrier material protective reagent is used in which the intermedium and carrier material are miscible (cf. on this subject the as yet unpublished application DE 10 2009 025 574).
Moreover, a process can also be used for this purpose in which carrier material or materials of different degrees of purity are used for different infiltration steps. The carrier material with the highest purity (i.e. with the lowest contamination by the intermedium) is used at the end (cf. on this subject the as yet unpublished application DE 10 2008 039 875).
Exposure of the user to harmful effects from process media and the like may, for example, also be avoided by adopting physical safety measures (cf. on this subject for example the as yet unpublished application DE 2008 039 876).
On the basis of the characteristic values or process parameters explained hereinbefore, for example a concentration of an alcohol solution or a temperature of the paraffin, the expert user can theoretically judge whether the embedding device is in a functional state. However, as far as the routine user is able to tell, if at all, such a judgement in current tissue processors is difficult and laborious.
With the embedding devices currently available for microscopic samples, in the event of a fault an error code is entered into an error protocol. The user has to select (call up) this error code in software, generally using sub-menus, and then decide whether measures are to be taken, and if so which ones. However, such an evaluation can only be carried out by trained staff with their specialist knowledge. Searching through sub-menus for an error code proves to be laborious and complicated.
For the user, the error detection described above is not very user-friendly. Therefore, in routine operation the functional state of the embedding device is often ignored, which may lead to a deterioration in the sample quality, adverse health effects and/or damage to the equipment.
There is a need for a user friendly display of system states of automatic treatment devices for microscopic samples based on detected system parameters enabling a user to react quickly.